Mark Mullin mark@vibrant3d.com said:
So I put in my vote for the concerns that have been addressed by Mono and wonder if anyone has any comments on the X11 license, since I spent grand total of 5 minutes looking at it and IANAL.
There's two kind of open source licenses, and the Wired article neatly summarizes them at the end. On the one hand, you've got the 'political agenda' licenses like GPL that mandate that every derived work is open source as well - this viral clause ensures that no-one can "hit-and-run", like Microsoft did when taking the BSD TCP/IP stack for their latest Windoze systems. On the other hand, there's the 'here is some source code, be happy with it' license, that is more relaxed about this possibility. The latter license is distinctly more attractive to commercial firms, because they have the possibility to mix open source and proprietary code and bring that out as a closed-source product.
Then, there's the middle ground. I think it started with the GNU Library/Lesser GPL, that allows the combination of LGPL and non-LGPL code in a restricted way. It works well for shared libraries, for example - linking to an LGPL'ed shared library doesn't create a derived work according to the license, which makes distributing proprietary software possible under Linux. The Squeak License also takes this middle ground. It is 'viral' in that modifications to the virtual machine or the base Smalltalk classes must be shared, but at the same time allows you to do whatever you want with the code you add to that. I think it is a very practical and reasonable middle ground, and meshes well with how you feel about what you will and what you will not contribute.
The Jini Community follows much the same model although it's not open source (you can only share with other licensees, but becoming a licensee is a matter of accepting a click-through license). Richard Gabriel and Ron Goldman developed a pattern language around the idea of a community that shares common code, but at the same time wants to compete with non-common code. I think large parts of it apply to the Squeak Community as well, so everyone should read it. You can find it at:
http://jini.org/JiniCommunityPL.html
(Philosophically, I'm all in favor of the GPL, but that's because I think that intellectual property has outlived its usefulness (if any), and that's an alltogether different discussion).