In Quebec, language law (bill 101) is enforced by the Quebec Board of the French Language. They have information on their website regarding many questions that are generally asked about the bill 101 and its consequences on business. They can be contacted for more details, and they are the authority in this matters.
I think those are the main points that can have an impact on a business in Quebec :
Bill 101, article 5 (Consumer part of the law) states :
Consumers of goods and services have a right to be informed and served
Not translating something in your product that can be read by a consumer in Quebec opens the door for legal consequences. Most of the time, the board will let you correct the situation before going to court.
Bill 101, article 4 (Worker part of the law) states :
Workers have a right to carry on their activities in French.
This means that a worker working in Quebec with your sofware has a right to ask his employer to provide him a translated version (or even an alternative sofware) in french. If you are not employing anyone in Quebec, you are not concerned directly by this law. But your clients may be. A Quebec government agency will always ask you a french version for its workers. Business partners of quebec government agencies may as well be bound by the same requirements (a la GPL).
Yet again, the board will always give you some time to adapt your processes, especially if you are working in R&D, or have mainly english speaking clients / partners (french link - summary : there are recuring debates about the language used in R&D companies in Quebec like Bombardier Aerospace. Some of them have long running exemptions because of their activities and/or clients.).