Practice at other companies I've been at has been that using GPL software on the server side (e.g. not distributed at all) was okay, and didn't taint our code or IP.
However, there are a lot of people who get very nervous about this when it comes to a potential acquisition of a company, and a worry that any use of GPL'd code (not distributed, just used) might be an issue for any potential acquirer.
Can someone point to some definitive information on this? Thanks...
I think you answered your own question. The GPL is very concerned with distribution, but very lenient with use. As long as the use stays in-house, You won't have to worry about FSF's huge pack of lawyers coming after you.
...oh wait.
GPL shouldn't be an issue if the acquiring company just wants to continue with in-house use.
If it is planning a different strategy and wants to distribute the code, it will either have to:
Neither of these are insurmountable. 1. may not even be an issue if the acquirer doesn't mind distributing under GPL terms (just look at Red Hat if you want an example of a company that sells GPL code very effectively....). 2. may cost money, but is usually pretty feasible, especially if the GPL components are only a small part of your code base. Also you will find that many libraries are actually LGPL rather than GPL, which is even less restrictive.
A lot will depend on who might be buying the company, and whether the primary aim is to sell the company or not, how tightly your code is dependent on the GPL code, and whether you have customised the GPL code.
I have run into a number of companies that have absolute "no GPL software" policies - typically these are companies from an embedded background, and it will (at best) take some effort to explain why the GPL is not such a problem on server side software.
You can probably also expect a higher level of technical due diligence than if you were not using GPL software - when an acquirer is being expected to pay out a large sum of money, they will want to be sure whether or not your software is a "derivative work" of the GPL code or not.
Another potential issue would be that you may well be unable to give a potential acquirer a copy of your code to look at prior to the acquisition - as in the general case this would count as "distribution", and you would then either have to give them the whole code under the GPL or be at risk of the copyright holders of the GPL code suing you for infringement.
Your company will have to assess the risk for itself, and if it is actively trying to sell itself then this should be done as soon as possible.