LGPL does
exactly what you want. You are free to use it for everything,
but you have publish the source, if you modified it and released it to
the public. IIRC LGPL is compatible with every open source license.
I made it GPL. At the GNU site, it says not to use LGPL for most purposes.
I don't know exactly what LGPL does. Unless I can't use GPL software to make
commercial music with, than I will use LGPL. I want this to be useful to the
Open Music scene so people can make open music but still be able to sell their work.
That was my only concern. It is just toys but hey, I think a TB303 is a toy,
and people use it for fun and profit too. But, it's NOT a TB303 clone, because of
copyright reasons... :)
LGPL is a less strict GPL, which is often used for libraries. If you
link against a GPL library your program have to be under the GPL license
(or BSD style license). If you link against LGPL, you can use whatever
license you want or closed source (see post from paul).