Deny use of my library to compete a certain company

Question

I'm developing a library for reading/writing a file format of a program created by a certain company. The guys from that company were so kind that they provided me with a documentation for their format, which I'm really grateful for.

I'm intending to release the library as open-source under a license "derived" from MIT, the difference being that the library must not be used to create a program that would compete with the original program, as an expression of my gratefulness to the company.

What I'm asking: is adding this rule to the license legally possible?

Answer 1

Instead of trying to add such a restriction, you could alternatively make your library GPL, or dual-licensed - GPL & commercial, with an individual pricing for each one who want to use the commercial version.

That way it will still be possible for someone else to write a competing open-source software using your lib, but it will typically discourage bigger commercial vendors. When someone is really going to buy your lib, you can still decide in each case whom you will sell the lib for a moderate price, or whom you will make an offer so expensive he won't buy it.

Answer 2

It is legally possible to add such a restriction to your license, but I would strongly advise against it.

1. Such restrictions take the license out of the realm of open-source software. All commonly accepted definitions of open-source disallow such restrictions on the usage of the software.

2. Drafting such a restriction so that it would hold up in court is hard and the gain is very small.

If you were given the specifications for the file format without such strings attached, then the chances are that the company feels secure enough that they don't fear competition from others that can work with their file format. Thus there is no need to restrict the usage of your library.