Basically, I only care that you do not remove the Copyright notice from the source code when using Sglib. More precisely: you can use Sglib or its derivative forms (under the condition that the Copyright notice is preserved) in any project, whether commercial or not, free of charges. In particular, you can use Sglib under the terms of any license defined as an open source license by the Open Source Initiative (see http://www.opensource.org/). This includes most common open source licenses such as the BSD license and GNU GPL. If you need to use sglib under any particular license conditions, contact the author.