Encyclopaedia of Chess Openings

Yes, it often is best disregarded.

"... For new players, I cannot recommend books that use [an encyclopedic] type of presentation [of opening theory], because the explanatory prose that elaborates typical plans and ideas is usually absent, thus leaving the student without any clear idea why certain moves are played or even preferred over other apparently equivalent moves. ... For inexperienced players, I think the model that bases opening discussions on more or less complete games that are fully annotated, though with a main focus on the opening and early middlegame, is the ideal. ..." - FM Carsten Hansen (2010)

Is encyclopaedia of chess openings available free for download ?

yes, it is. www.indianchess.org/yahoo_site_admin/assets/books/eco-codes.pdf

Or if you're suspicious about this, you can see an overview on Wikipedia: en.wikipedia.org/wiki/Encyclopaedia_of_Chess_Openings

And how out of date is that all by now...?

Well actually I was talking about these books.... images.app.goo.gl/nkvtMvnafN6Su69E6
I mean are they available free for download ?

I have five ECO A-E paper Volumes dated from 1978 to 1984 and I admit to still using them??!!!! Plus also use BCO I (1982)
and II (1989)!!??
However, I do supplement them with other current database resources.
SO There!