The Collaborative International Dictionary of English v.0.48:

Open-hearted \O"pen-heart`ed\, a.
   Candid; frank; generous. --Dryden. -- O"pen-heart`ed*ly,
   adv. -- O"pen-heart`ed*ness, n. --Walton.
   [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

93 Moby Thesaurus words for "openhearted":
   amiable, artless, bighearted, bluff, blunt, born yesterday,
   bounteous, bountiful, broad, brusque, candid, childlike, confiding,
   cordial, direct, downright, explicit, forthright, frank,
   frankhearted, free, free-speaking, free-spoken, free-tongued,
   freehanded, freehearted, friendly, generous, genial, genuine,
   giving, gracious, greathearted, guileless, handsome,
   heart-to-heart, hearty, hospitable, ingenu, ingenuous, innocent,
   large, largehearted, lavish, liberal, magnanimous, munificent,
   naive, neighborly, open, openhanded, outspoken, plain,
   plain-spoken, princely, profuse, receptive, round, simple,
   simplehearted, simpleminded, sincere, single-hearted,
   single-minded, stintless, straight, straight-out, straightforward,
   transparent, trustful, trusting, unchecked, unconcealed,
   unconstrained, undisguised, undissembled, undissembling,
   unequivocal, ungrudging, unguarded, unreserved, unrestrained,
   unselfish, unsophisticated, unsparing, unstinted, unstinting,
   unsuspicious, unvarnished, unwary, warm, warmhearted, welcoming