In terms of this problem, having been working now with a "joomla solution" for about 6 months I would like to make these observations:
1. Integration is a loose term here. What we really should call it is single user login module (and its concomitant user table synchronization). This reflects what part of the integration we are talking about.
2. Integration at another level - look and feel, seamless integration of multiple cms platforms for a single user experience - is not so easily achieved, nor guaranteed just by having the login feature solved.
3. The issues of hacking all the user login / logout / profile information and links OUT of the PKP platforms is an issue for many people because one has to get right into the code to do it. With joomla, one merely turns these controls on or off as needed. So even once single signon has been achieved, synchronization of the users across all platforms has been achieved etc, there is still some work to go and this is NOT something one can put into a plugin or an addon in any respect.
4. Integration, as my blog response suggests (http://pkp.sfu.ca/quickstudy5
) can include iframes within Joomla such that PKP content lands nicely inside the main content area of a joomla implementation, thus achieving a pretty good level of integration - there are very few issues connected to this approach, but the work related side is that one must learn how to control links to each and every PKP content page and port them into the joomla menu structure. This is not difficult, but it does take time.
5. Integration of joomla within PKP seems to me to be virtually impossible, if not undesirable, so I won't even venture into that area.
Another interesting approach to this question has been one where a designer has taken a fairly sophisticated Joomla template and hacked it INTO a PKP theme. This seems to me to be an interesting solution on ONE level for many people. If this works within reason (as seems to be the case I have seen) then it is possible to create two separate independent platforms running along side each other, more or less having the same look and feel, utilising a user synchronisation for dual login, all without giving up most of what comes with PKP and adding into the joomla those aspects that are wanting or missing from PKP altogether.
In my experience, a JOOMLA/OJS integration would benefit mostly from this approach, but less so a JOOMLA/OCS - or all three.
I am currently building up three examples of what I am talking about, but as production sites.
a) a complete joomla/ocs/ojs integration through a single joomla template, which intends to provide seamless integration of a an organisation, its conferences and OJS for publishing conference proceedings (although it could be a standalone journal)
b) an non-profit organisation website which will provide dual login between an very developed Joomla web through to its Boletin (OJS) and later a conference website (OCS) keeping the 3 platforms independent but hacking the templates so that they provide a similar look and feel.
c) A Joomla / OJS integration under one template. This one has 30 back issues so it is on the backburner at the moment.
When I think they are ready for viewing I will post their locations and see if I can create a demo version of each for testing purposes.The bottom line: Venturing into integration of PKP with other open source CMS converts the project from the main lines of a CMS (ease of use, for example) back into a PHP programming mode (hacking core code, adapting, bypassing, implementing new codes) so it is a decision which literally puts us back into dependency upon secondary services (designers/programmers/technical support).
If you have that level of support, then it can be done.
If you are an "on your own" novice CMS user just trying to get your publication up and running and would like a quick fix integration with Joomla then I'd say reconsider!