Using a license that prohibits commercial usage (which, by the way is VERY hard to define) than GPL will make your software incompatible with all existing libraries and programs that use that license. It also means that it will not be included in software like R or in linux distributions like debian.
I know different programs which used some kind of noncommercial license and which was not maintained for this reasons: you can not link the software to most other libraries or utilities.
If you use the GPL, and someone will sell products using or based on your code, they are obliged to give access to the full source code. That means including all their modifications and all other code for their program. I think that's a fair deal: improvements and new possibilities become available.
Since you are the copyright holder, you can also decide to have both a GPL version and a commercial license: in reality people selling software will want a license which does not force them to publish their whole program under the GPL. They will happily buy a license to get rid of that restriction. This is a scheme which among many others is used by oracle for berkeley db:
Thus, the license depends on how a particular application that uses
Berkeley DB is distributed to the public. Software that is not
distributed can use the Sleepycat License, as can free and open source
software. Proprietary software can use Berkeley DB only under a
commercial license agreement between Oracle and the application's
A last thing: it is very hard to define 'commercial usage'. Is a PhD student working on a project using your software commercial usage? His wage is paid by the project...
One last thing to convince your team leader:
Releasing code under the GPL leaves only the same opportunities for
(legal) commercial gain as does publishing a journal article
describing some method or process that can be exploited commercially.
From this similar question on Stackoverflow. And in fact it is not true: if you publish an article, the publisher will usually claim the copyright and the revenues of the article, so you are better of using GPL than publishing it in a journal.