Licensing is though topic. I tried to explain some of the upcoming rsyslog license changes with yesterday’s blog post. While I tried to cover all aspects, I have probably manged to create some confusion. I try to cleanup this mess today. In doing so, I will leave out some of the fine details but focus on the prime visible facts.
First of all, the rsyslog project as whole will stay under GPLv3. If you dig down into the details, the current version is licensed under GPLv3, with a large body of code (the rsyslog runtime) being licensed under LGPLv3. In straight words, this means that rsyslog as whole can not be included in a commercial product while the rsyslog runtime can be. So if someone intends to provide rsyslog-like functionality, he or she can use the runtime and rewrite the rest of the system (but not copy it). Also, it is possible to create commercial rsyslog plugins with the current system, but then one relies either on a “creative” interpretation of the GPL or use message passing e.g. via pipes between core and plugin.
With the intended changes these basic facts, in regard to rsyslog as whole, are not changed at all. However, the details change: the body of code that is licensed under a permissive license (allowing use inside commercial applications) will be increasing. Still, some key files will remain under GPLv3, and so will the overall rsyslog project. Also, in the future the permissive license used by rsyslog will probably be the Apache software license (ASL 2.0). This open source license is used by a myriad of well-known software products, with the Apache http server being a prime example. It is not sure if ASL 2.0 will totally replace LGPLv3 inside the rsyslog runtime, this depends on contributor reactions. For many of the same reasons, it is also not yet clear what exactly the GPLv3 core of rsyslog will be.
Why is this change benefitial to the project? Maintaining and developing rsyslog is costly. In the typical open source business model, these costs are covered by the sales of project-related services. Unfortunately, the rsyslog project received relatively little funding via this way and is still heavily sponsored by Adiscon, which can not bear the majority of the cost for all time to come.
One problem with receiving funding is that some potential customers – especially large ones who could considerably contribute to funding – do not like to license under GPLv3 for one reason or the other. One “solution” to that problem would have been to dual-license rsyslog in its current form. We actually considered that (blog posting) but stepped back from the initial approach after discussion with key community members. As described in the mentioned blog posting, it would not have been very hard for Adiscon as the main copyright holder to change the licensing model. However, this would probably have meant that a commercial and a non-commercial fork of rsyslog would have been created with potentially large differences in the code base.
The move of more code under a permissive license prevents this problem. With the new model, only relatively few key files would need to be dual-licensed. This prevents large diversity inside the code base just for licensing reasons. Also, the ASL is far more appealing to many large users, so we hope to gain additional deployments – and thus potential customers – from that move.
Finally, this model facilitates the ability to provide commercial plugins. Commercial plugins were always OK with the project, and as said above, can even be written and distributed under the current licensing scheme. The new licensing scheme makes it easier to support such plugins and encourages technical superior solutions. How exactly the licensing in this regard will be is not yet fully thought out. One solution might be to add a special exemption to the then-smaller GPLv3 core, that explicitely permits plugins (getting the wording right may be somewhat tricky). Another one is that someone who intends to ship commercial plugins must rewrite the rsyslog GPLv3 core, which is no longer that hard even for external entities as the GPLv3 core is smaller (one may argue that Adiscon as the main contributor has an advantage here over others; I can’t decline it but I don’t find it unfair either – after all, Adiscon has spent considerable effort on rsyslog, so why not reap a small benefit in this situation?). These solutions are the extreme ends of the solution spectrum – it could probably also be anything in between.
Why is this useful to the community? Obviously, the changes help fund the project, and thus help to keep it not only maintained but well-enhanced as well (there are many cool things I have on my mind, but the current time constraints do not permit me to work on them). This is even more important as the journald project will create a new, mostly commercial, environment for rsyslog. In the future, rsyslog needs to compete with syslog-ng primarily in that part of the Linux ecosystem. Balabit, which traditionally dual-licenses syslog-ng under a proprietary license has a big advantage regarding this customer base from that fact alone. So far, rsyslog could make up its disadvantage by the fact that it was installed on each system, an advantage that journald will very probably remove from rsyslog. The other benefit is that the more permissive licensing model will probably attract additional software vendors and maybe additional parties, especially if we can move the full rsyslog runtime to ASL. There seems to be a movement inside the industry towards this type of licenses, at least for projects playing in the enterprise environment. If all works out well, we may even get some more contributors and thus the ability to include additional features into the project.
In short, the licensing change will not affect that much of what actually can be done with rsyslog code, but it provides rsyslog with some additional options that benefit both the project and the community.
I hope I have expressed myself clearly enough this time. Again, it has become a long post, even though I omitted some detail information given in yesterday’s post. Licensing obviously is tough ;) I hope to soon be able to use my time for more productive things, again…