"Falle bod nhw'n barod."

Translation: Perhaps they are ready.

[MatthewSke1]

Is this use of "bod" similar to the subjunctive tense in other languages?

[ibisc]

It is just the usual way of introducing an unemphatic noun clause in the present or imperfect:

• Efallai bod nhw'n barod i fynd adref - Perhaps they were/are ready to go home
• Wrth gwrs bod nhw'n barod i ymddiheuro - Of course they are/were ready to apologise
• Ro'n i'n gwybod fod e'n barod i ymadael - I knew that he was prepared to leave

The construction is similar for noun clauses in other tenses:

• Ro'n i'n meddwl byddai fe wedi prynu car newydd erbyn diwedd y mis - I thought that he would have bought a new car by the end of the month
• Rydych chi'n gwybod bydd hi'n prynu cinio i ni i gyd ym Mhorthmadog - You know that she will buy lunch for us all in Porthmadog.