There is much discussion about What ALT.NET really stands for. Most of the things discussed were very "fluffy" in their description and mostly meant some state of mind and openness. Here's another possible explanation:

We are uncovering better ways to develop software as Microsoft oriented developers:

The Rule of Composition

• Compose your development tool set with just enough tools to make your job easier
• Always check to see if you can enhance your productivity, quality of work or confidence in your work by adding to or replacing a tool your are working with.
• Tools are not an end. they are a means to an end.
• Languages can also be considered as tools
• Do not stay still in your knowledge.

In the end, a composition of tools can provide a better X for you or your team where X could mean:

• Maintainability
• Quality
• Readability
• Confidence
• understanding
• productivity
• Communication

De-Composition can also lead to a better X. Removing a tool that prevents you from doing your job or replacing it is advisable if you feel that is what's needed. In  any case, always challenge your assumptions about how productive, confident or good your are as a coder. Reach out and read, learn and try other options.

Tools can also be frameworks, plugins, languages, knowledge, patterns and approaches to existing problems.