If yes, what precautions should I take?
With an MIT/X11-licensed product:
- you CAN:
- re-use the code freely for your own use,
- re-use the code freely for non-commercial AND commercial re-distribution, whether in source or binary form.
- you CANNOT:
- claim authorship of the software,
- thus you cannot attack the original author for using or publishing his original version.
So, yes, you CAN use MIT/X11-licensed plug-ins in your commercial application.
MIT/X11 is basically a simple contract that says:
- Person or company X created Y.
- Y belongs to X, but X is granting you the right to use it and do whatever you want with it.
- X cannot be held accountable for anything that goes downhill with what you do with Y.
The MIT license allows you to
use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software
as long as the license text (copyright notice and disclaimer)
shall be included in all copies or substantial portions of the Software.
Where does this license text have to appear?
Having MIT-licensed software work server-side (e.g. as a PHP script) to produce a HTML page is not redistributing the software, unless the program includes itself in its output.
The full text of the MIT License can be found here.
I'm not a lawyer, but it seems like you can
deal in the Software without restriction
even so far as
distribute, sublicense, and/or sell copies of the Software
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
Again, I'm not a lawyer, but you might fulfill that condition via comments in all pages or scripts that use the MIT licensed plugin or an Acknowledgments page.
Every opensource licence to date (MIT too, a BSD-spirited licence) allows you to use the software on a commercial web site (and that's part of the reasons for the extreme OSS propagation in latter years) with some notable exception. Those exceptions are: