Is Python software saleable?

Is Python software marketable?

Of course.

Or will my code be seen purely legally Open Source Code?

No, how do you get the idea? You got it PSF license read at all?

(Apart from this: you can also ask for money for open source software and market it. However, the business model is usually one for support and binary distributions because the source code itself is freely available.)

Is it possible to sell a program written in Python on the basis of Trademark Python?

Of course. You don’t write Python, you write software with Python. The copyright remains completely with you, you don’t have to take over the license of Python.

What you need to look after:

• Licenses of dependencies, i.e. libraries used by your software. They are usually also uncritical, but sometimes you have to fulfill certain requirements (for example, mention in the documentation). In some cases, there could be libraries that forbid commercial use or are “infectious”, i.e. the software they use as “derivative works”. This is very rare.
• If you deliver a Python runtime environment with your software to the customer, could be who have another license. One example would be ActiveState Python.

This is not only true for Python. Virtually every significant programming language is defined by a community today and has an open source reference implementation.