[Reelin]

Yes, I believe the MPL fits the usecase you describe.

As far as I understand it, proprietary code using an LGPL licensed library is more or less incompatible with templates in header files (!!!) since there's no way (AFAIK?) to relink against a modified version without providing your full source code. Supposedly the LGPLv3 provides an exception for header files but personally I wouldn't go anywhere near it because it seems quite vague - "small" macros, templates that are less than 10 lines (what constitutes a line?) etc.

So as currently licensed (LGPL), I don't think your library is usable as part of a proprietary project.

The MPL, in contrast, places no relinking requirements on the developer. You only have to share any changes you happen to make to the MPL licensed code.