Connor Essam's move to Leyton Orient is complete after the Sky Bet League 2 side agreed a fee with non-league Dover.
Midfielder Danny Guthrie has become Blackburn's third signing of the summer.
Cywka's current deal expires this summer and the Tykes were keen to tie down the Pole to a new contract.
However, both parties have failed to agree terms and the 25-year-old seems set to leave on a free transfer.
The news is sure to alert a host of clubs to the availability of the former Wigan and Derby man.
Cywka made 52 appearances and scored eight goals during his two-year spell at Barnsley.