Be very careful that you do not use copyrighted source code for which you do not have right, which includes open source licenses like the GPL in your proprietary codebase.

When the time comes for your company to be purchased, it's likely that the acquirer will scan your source against known OSS codebases. There are companies whose entire business is to perform these scans for potential acquirers.

If they find a match, it raises red flags and the acquirer could walk away. Buyers get uneasy when it appears they may not actually own what they're buying.