At choosealicense.com/licenses I am reading the Apache licensing, and see that under Permitted there stands Commercial Use:
This software and derivatives may be used for commercial purposes.
Meaning, they can use (and modify) my app, in a commercial environment (e.g. Microsoft, Apple). Or, they can commercialize my app? English is not my native language and I am wondering if I am misinterpreting something.
Best Answer
Commercial use is any use that is a part of revenue generating activity, that is, making money. It includes all use by for-profit organizations (companies) and use by self-employed natural persons as part of their paid work.
It has nothing to do with the environment. Using Linux to run a web shop is a commercial use and using Windows at home for watching youtube videos is not commercial use.
This is in contrast with licenses that allow free use for some purposes, but require fee for commercial use. Such licenses are not considered open-source and note that the site does not list any license that would not permit "commercial use".
This does not imply that they can derive commercial software, i.e. one where fee is required for use, from your work. However the Apache license does permit that. It is the "sublicense" item, last one in the permitted list.
The "sublicense" in general means that the recipient of the work can further distribute it or derived version under different terms. Which specifically includes requiring fee for use. GPL prohibits this and requires that derived work may only be distributed under the same license while most other open-source licenses permit it.
Note that even GPL-licensed software can be sold, but it's the distribution itself that is paid (e.g. burned CD with Linux can be sold) while the recipient still gets the right to use it for any purpose and most importantly to further distribute it.