This question keeps turning up and it is my belief that many journals would not approve of any other “publication” without their consent and this can potentially cause legal issues. You would be advised to liaise with the journal I think.
There is an explanation of ResearchGate IP policy at https://www.researchgate.net/ip-policy
The legal possibility of uploading an article to your RG profile depends more on the journal terms and conditions than on RG.
In general, you can immediately publish in RG a pre-print of your article (i.e. a version prior to the peer review). The final version (as published in the journal) of your article can be uploaded when the corresponding embargo period has ended (usually 6, 12 or 24 months).
If it is an open access publication, you will have no problem publishing it at any time.
To clarify what your rights are on the article, I recommend reading the terms and conditions that you accepted when you authorized the publication of your article.
On this website there are other alternatives to share your article: http://www.howcanishareit.com/
Here published with copy right transfer 'term' seems to be important point. I think one should consider the terms and conditions before taking any action.