Bóg, not Bug. "Bug w domu" would be rather unpleasent situation
It's actually "gość w dom, Bóg w dom". It's one of the many greeting phrases.
It isn't a greeting phrase (at least nowadays). It's a proverb.
There is (or was?) however a traditional slavic custom to welcome a foreigner with bread and salt.
Not only foreigners :):
It's an old Polish custom, but nowadays it's usually reserved for special (and rather official) occasions, like a wedding or arrival of someone important.
Or "Gość jest Pan Bóg w domu."
No such thing. It's an old Polish proverb and it's only and always "Gość w dom - Bóg w dom.":Each meeting consists of people, " the peace " and " political " in the Polish gentry strictly based on certain principles of politeness , especially when it took on an official character . Especially during the visits had to comply with the various formalities established , which were part of the unwritten code of social past.
It was the custom of old and widespread that in the common master, as well as in a peasant 's hut simple , always lay on the table bread and salt , which greeted guests at the thought of words contained in the title text. In many homes was also a habit of leaving a few free places at the table for men " Zagorskis " that may come up unexpectedly . Who came only in the thresholds home with a sword at his waist - a man of the knighthood , and gave honor to the host , had the right to sit with him to the table. For good tone should also expect visitors , especially when the visit was announced . Watch for them then in the morning , and many homes were sent up to the roof servant to this urgent follow if the guest arrives . When the servant gave to know that the vehicle is approaching from the guests to the house , everything that lived , was moving in greeting. A sign of respect was a photo of the cap, which is often accompanied by a beautiful bow. It was low , and the host put his left hand on the heart, the right and headed toward the ground . Welcome and farewell social was often the kiss , which was dependent on the situation , people and their age. The fashion was also kissing the hand , but used it only for older people . Mostly kissed the hand of elderly matron , serious ladies , very rare adult virgins .
When Poles greet guests they usually say "Witamy!" (or doubled: "Witamy, witamy!" :)) or simply greet them with "Hello", etc. If the guests aren't close family or people you know well Poles may also add "serdecznie" and it's going to be: "Witamy serdecznie", for example.
As I know it exists only in this form "Gość w domu, bóg w domu"
The correct version (or at least most commonly used) is the old Polish version: "Gość w dom - Bóg w dom". Without "-u" at the end.