LPT: If ever you need a program you want for free (for example a video/photo editor) don't search for "free", search for "open source" to avoid limited trial versions, adverts and malware

The reasoning being if you type "free", generally you will be advertised to or get the LITE version which will only have some of the functionality and then will be up-sold to.

Open source does what it says on the tin - the code is open for anyone to examine and even adapt and is usally available in-full for free, occassionaly accepting donations if you are so inclined.

This has the added bonus of ensuring there are no nasties like crapware or reporting your user history back to their servers etc. because open-source equates to peer-reviewed and open to be examined by anyone.

EDIT: just because it was mentioned, being open source doesn't MEAN that a program is virus-free, but it is a substantially lower risk than closed-source software. Either way, you would be better off with open-source in general.

I am assuming you will be excising a modest amount of caution with what you download by checking it against trusted reviewers/communities.