If you're talking about the installation executable files - i.e. what you run when you install the software - you can do pretty much as you wish. I have copies of e.g. Office saved to an external hard drive and to a couple of DVDs as well, just for safety. Backing up/copying (there's really no difference) your programs in this manner is entirely legal and doesn't count as an installation. And, in fact, absolutely should be done.
How to get Windows 10 now: how to download and install Windows 10 even if GWX.exe is missing