William,
Thanks for the clarification! You asked if the link I provided was secure. It's that of Malwarebytes. I would trust it above all else.
Software at many download sites these days come bundled with Potentially Unwanted Programs (PUP). Download.com is one of them, along with quite a few other sites which used to be popular.
'Also,can I configure the program to only run on demand so as to not interfere with my main antivirus program which is currently the latest version of Avast Free?
In your original post you noted you "would like to consider installing Malware bytes free edition to run scans on demand. Does the free edition allow this or does it run continuously in the background?
To clear up any confusion, here are the differences between the FREE edition and the PAID Premium:
https://www.malwarebytes.org/antimalware/ ⇐ In short, the FREE version ONLY runs on demand, while the PAID offers real-time protection.
NOTE:
•The free version comes with a 14 day trial version of the paid, which is installed by default. IF you don't wish to try the trial version, it's necessary to UNcheck the box next to "Enable free trial of Malwarebytes Anti-Malware Premium" on the final screen where you exit the setup. Otherwise, see their "General Questions" where they note how to revert to the free version (Question #5)
• If you encounter any problems as a result of remnants leftover from the previous install, run their Clean Uninstall Tool I would run it first.
Best of luck..
Carol