Is there a way to start vim in read only mode

See $ vim --help for Vim's many launch arguments.

For launching Vim in read only mode that would be:

$ vim -R filename

EDIT

$ view and $ vim -R seem to be one and the same by way of symbolic links. I'm not sure what features you'll gain from running $ vim -R that you don't have with $ view.

Here, on Ubuntu, I can visually select stuff in both.

If you forgot the -R option when start up vim, you can use:

:set ro

If your goal is simply not to overwrite the original file, you can vim's read from stdin feature:

cat filename | vim -