I was noticed that using Open source is dangerous, because some Open Source could be allowed only for Open Source projects. So my project is "For sell" and I'm scared using it...
Can someone tell me : Can I use NPOI in my commerce project ?
And maybe someone can clear my fears of using open source libraries and open source at all...
Thank you.
It's under Apache license, so yep you can. You should always read the license though, and talk with a lawyer if you have any doubt.
Well I don't know if I'd say that it's "dangerous". It is, after all, free. As with any other software you use, commercial or otherwise, you should make sure that you understand your legal obligations.
That particular project appears to bear an Apache license, which means that it should be "safe" to use as a basis for your commercial software. However, you definitely should work with an actual lawyer for real advice.
NPOI authors offer you this terms: apache license. You should consider them carefully. Only you can tell if those terms are acceptable for you.
This text is not very long and not that complicated. Consult your company lawyers if you aren't sure what some phrases mean.
By the way, the opposite of "for sell" is "free of charge", not "open source". Giving your users open access to the source code and taking money from them - two different things. Doing one doesn't stop you from doing the other.